1. Field of the Invention
The present invention relates to a heater preheating device, and more particularly, to heater preheating device for a cathode ray tube adopted to facilitate advanced normal operation at an initial state when turned on.
2. Description of the Related Art
As is well known in the art of contemporary practice for heating up a cathode ray tube, at an initial state when turned on, it takes six to seven seconds to activate a visually emergent image on a screen in normal operation. To activate a cathode for a beam forming operation in a cathode ray tube, a heater must be heated up promptly when power is supplied. Thus, a cathode ray tube is in an abnormal operational state until its heater is sufficiently heated up.
Earlier monitor driving devices include a power supply for supplying power to a computer, a computer circuit operated by the power supply and outputting a video control signal for operating a corresponding device and a monitor operated in response to the control signal outputted from the computer power circuit. The power supply includes a computer supply for supplying the power to the computer circuit and a monitor power supply for supplying power to the monitor in response to a monitor power control signal on the computer circuit.
The monitor includes a monitor circuit operated in response to the power supply from the monitor power supply and the video control signal from the computer circuit and a cathode ray tube (i.e., a CRT) control signal applied to a corresponding device and a cathode ray tube receiving the power from the monitor power supply and operated in response to a cathode ray tube control signal from the monitor to a circuit.
When power is supplied to the power supply, the monitor power supply supplies the power to the monitor circuit and the cathode ray tube. The computer power supply supplies the power for operating the computer circuit. When a video control signal is inputted to the monitor circuit from the computer circuit, the monitor circuit outputs a cathode ray tube control signal to the cathode ray tube signal and is operated in the video image signal corresponding to the video control signal from the computer circuit.
In the earlier monitor driving device, the power consumption by the monitor can be reduced by the monitor power control signal from the computer circuit. The computer circuit outputs a monitor power control signal at a low level to the monitor power supply to reduce the power consumption by the monitor. The monitor supply cuts off the power to the monitor circuit and the CRT, thereby reducing the power consumption while the monitor is not being used. The monitor control signal at high level is from the computer circuit to the monitor power supply to use the monitor again by operating the monitor circuit and the cathode ray tube in which the power was previously cut off. We have found however, the earlier monitor driving device has a disadvantage in that it takes too much time to display the image on the screen of the cathode ray tube due to the heating time of the cathode ray tube when the monitor driving device is turned off by the monitor power control signal and again turned on by the monitor power control signal at the high level after the passage of a predetermined time. We have also noticed that the earlier monitor driving device has another disadvantage in that the life span of the cathode ray tube is reduced when the voltage is continuously applied to the cathode ray tube to preheat the cathode ray tube.
Recent efforts in the art such as the patent to Song, U.S. Pat. No. 5,483,464, entitled Power Saving Apparatus For Use In Peripheral Equipment Of A Computer, is but one example of an apparatus for turning off peripheral equipment (such as a monitor) in a computer apparatus to save power in a stand-by state. The Walker patent, U.S. Pat. No. 5,335,168 entitled Computer System With Power-Down Mode For Monitor, endeavors to conserve power by powering down the monitor much in the fashion noted above. In addition, as illustrated in FIG. 4 thereof, a diode 70 is utilized to supply a lower than normal voltage to the filament 40 of the cathode ray tube to decrease the period of the time needed for the cathode ray tube to again be operated after being in a stand-by state. However, Walker does not teach or suggest the supplying of the power for the lower voltage being generated by the computer power supply rather than the monitor power supply as in the present invention.
Such an interval for warming up a heater may even deteriorate the utility value of an information that a user wants due to a failure of timely display on the screen of a cathode ray tube in the intelligent society of today.
In an earlier technique for supplying power to a monitor associated with a computer system, a power supply circuit includes a rectifier for rectifying supplied alternating current power and for generating a rectified direct current source voltage, a first power generator for receiving a direct current from the rectifier and for generating power in a at Switching Mode Power Supply SMPS mode, a first power supply, supplied with power from the first power generator, for supplying power to various circuits in a monitor, a second power generator, fed with direct current from the rectifier for generating power in a Switching Mode Power Supply mode and a second power supply, supplied with power from the second power generator, for generating power for use by a computer system.
The rectifier is supplied from a commercially available external power source with alternating current AC (110 Volts/220 Volts ), rectifying and smoothing the supplied power by using a combination of a diode and capacitor, generating rectified power at a constant voltage level of direct current.
The first power generator is supplied with a direct current and generates power in a Switching Mode Power Supply SMPS mode.
The first power supply is supplied with power from the first power generator and supplies power at different voltage levels so as to energize various circuits in a monitor.
The second power generator is supplied with direct current from the rectifier and generates power in a Switching Mode Power Supply mode. The second power supply is supplied with power from second power generator and supplies power at different voltage levels so as to energize various circuits in a computer system.
When an operation of a computer system is suspended for a predetermined time interval, the first power generator supplies no power to the first power supply upon receiving a power saving signal output from a microcomputer (not shown).
A Switching Mode Power Supply SMPS mode is known to a person skilled in the art so that no further explanation will be given to that terminology.
Upon observation of contemporary art as previously described, there is found a drawback.
That is, the first power generator is subject to receive a power saving signal to cut off further power generation when a predetermined time interval during which an operation of a computer system has lapsed into suspension or idleness.
As a result, when back to reuse, it takes a while for warming up a heater again which may result in loss of valuable information. Therefore there is an increased need for effective circuits that facilitate more advanced normal operation of a monitor at an initial state when turned on, thereby ensuring prompt use of a whole computer system.